MAX8903CETI+ Maxim Integrated Products, MAX8903CETI+ Datasheet - Page 21

• Manufacturer Part Number: MAX8903CETI+
• Description: IC DC/DC CHARGER LI+ 2A 28-TQFN
• Manufacturer: Maxim Integrated Products
• Series: Smart Power Selector™r

Specifications of MAX8903CETI+

• Function: Charge Management
• Battery Type: Lithium-Ion (Li-Ion)
• Voltage - Supply: 4.1 V ~ 16 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 28-TQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

VL is a 5V linear regulator that powers the MAX8903’s
internal circuitry and charges the BST capacitor. VL is
used externally to bias the battery’s thermistor. VL takes
its input power from USB or DC. When input power is
available from both USB and DC, VL takes power from
DC. VL is enabled whenever the input voltage at USB
or DC is greater than ~1.5V. VL does not turn off when
the input voltage is above the overvoltage threshold.
Similarly, VL does not turn off when the charger is dis-
abled (CEN = high). Connect a 1μF ceramic capacitor
from VL to GND.
Figure 7. Thermistor Monitor Circuitry
Table 3. Fault Temperatures for Different
Thermistors
Thermistor β (K)
R
Resistance at +25°C
(kΩ)
Resistance at +50°C
(kΩ)
Resistance at 0°C (kΩ)
Nominal Hot Trip
Temperature (°C)
Nominal Cold Trip
Temperature (°C)
TB
(kΩ) (Figure 7)
R
TS
R
THERMISTOR
CONNECTION
T
ALTERNATE
R
______________________________________________________________________________________
TP
THERMISTOR
CIRCUITRY
25.14
3000
4.59
10
10
55
-3
2A 1-Cell Li+ DC-DC Chargers for USB
R
TB
R
27.15
3250
T
4.30
10
10
53
-1
CEN
VL
29.32 31.66 36.91
3500
4.03
GND
THM
10
10
50
0
VL Regulator
VL
3750
3.78
10
10
49
0.74 VL
2
0.87 VL
3.316
4250
4.5
10
10
46
0.03 VL
0.28 VL
MAX8903A–
MAX8903G
MAX8903Y
MAX8903E
The THM input connects to an external negative tem-
perature coefficient (NTC) thermistor to monitor battery
or system temperature. Charging is suspended when
the thermistor temperature is out of range. The charge
timers are suspended and hold their state but no fault is
indicated. When the thermistor comes back into range,
charging resumes and the charge timer continues from
where it left off. Connecting THM to GND disables the
thermistor monitoring function. Table 3 lists the fault
temperature of different thermistors.
Since the thermistor monitoring circuit employs an exter-
nal bias resistor from THM to VL (R
mistor is not limited only to 10kΩ (at +25°C). Any
resistance thermistor can be used as long as the value is
equivalent to the thermistor’s +25°C resistance. For
example, with a 10kΩ at +25°C thermistor, use 10kΩ at
R
For a typical 10kΩ (at +25°C) thermistor and a 10kΩ
R
state when the thermistor resistance falls below 3.97kΩ
(too hot) or rises above 28.7kΩ (too cold). This corre-
sponds to a 0°C to +50°C range when using a 10kΩ
NTC thermistor with a beta of 3500. The general relation
of thermistor resistance to temperature is defined by
the following equation:
TB
TB
, and with a 100kΩ at +25°C thermistor, use 100kΩ.
ALL COMPARATORS
60mV HYSTERESIS
resistor, the charger enters a temperature suspend
MAX8903B/MAX8903E/
and Adapter Power
R
MAX8903G ONLY
T
COLD
=
HOT
ENABLE THM
R
25
×
e
⎧
⎨
⎩ ⎪
β
Thermistor Input (THM)
⎛
⎝ ⎜
THM
OUT OF
RANGE
T
+
273
1
THERMISTOR
°
TB
DETECTOR
C
, Figure 7), the ther-
−
DISABLE
CHARGER
298
1
°
C
⎞
⎠ ⎟
⎫
⎬
⎭ ⎭ ⎪
21